If your book is 600 pages long, you are demanding more of my time than I feel free to give. And if I could accomplish the same change in my view of the world by reading a 60-page version of your argument, why didn’t you just publish a book this length instead?
The honest answer to this last question should disappoint everyone: Publishers can’t charge enough money for 60-page books to survive; thus, writers can’t make a living by writing them. But readers are beginning to feel that this shouldn’t be their problem. Worse, many readers believe that they can just jump on YouTube and watch the author speak at a conference, or skim his blog, and they will have absorbed most of what he has to say on a given subject. In some cases this is true and suggests an enduring problem for the business of publishing. In other cases it clearly isn’t true and suggests an enduring problem for our intellectual life.
Sam Harris — The Future of the Book.